!"git ..." hopefully always succeeds because "git ..." is not the name
of any executable. However, that's not what was intended. Unquote
it, and while we're at it, also replace ! with test_must_fail since it
is a call to git.
Signed-off-by: Thomas Rast <trast@student.ethz.ch> Acked-by: Jon Seymour <jon.seymour@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>